자기열량효과 측정방법과 열역학적 관계식

이종석 국립7개대학공동논문집간행위원회 2002 공업기술연구 Vol.2 No.-

Magnetic refrigeration is based on the magnetocaloric effect(MCE) - the ability of some metals to heat up when magnetized and cool down when removed from the magnetic field. The available techniques for studying the MCE are: ⑴ direct measurements by monitoring the change in material's temperature during the application or removal of the magnetic field; and ⑵ indirect calculations from experimental data of magnetization and/or heat capacity as a functions of temperature and magnetic field. Thermodynamic relations used in calculating the MCE as adiabatic temperature change and isothermal magnetic entropy change are presented.

선체 변형방지 및 수정에 관한 사례 연구

박현수,염재선 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

Deformations during shipbuilding process make lower the buckling strength of structural members and decrease the quality of external appearances. So, it is required lots of expenses for the corrections. Many researches have been performed related to residual stresses and deformations for welded structures. However, it is not easy to find the studies about the prevention and corrections of deformations. The aim of these study is to investigate the locations and features, and to present the precaution and correction methods for deformations which are occurred in shipbuilding processes. In general, hull deformations are dependent on heating conditions and fabrication sequences. They can be corrected by controlling the above conditions and by applying external forces and various heating. These results can be used as a guidance during the actual hull construction.

모바일 환경을 위한 도식화된 지도 생성에 대한 연구

박동규,류동성,어윤 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

Location Based Services(LBS) are increasingly popular service on mobile marketplace. Although most popular mobile devices are mobile handset and PDA, they have relatively small display device. Therefore original terrain map should be simplified and schematized for mobile environment. We describe the design and implementation of this kind of schematic map generation system with icon and label, which is realtime system for automatically designing and rendering schematic maps.

적응관측기를 이용한 SPMSM의 속도 및 위치 센서리스 제어

정택기,이정철,이홍균,정동화 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

This paper is proposed to position and speed control of a surface permanent magnet synchronous motor(SPMSM) drive without mechanical sensor. An adaptive state observer is used for the mechanical state estimation of the motor. The observer is developed based on a nonlinear model of the SPMSM, that employs a d-q rotating reference frame attached to the rotor. A adaptive observer is implemented to compute the speed and position feedback signal. The validity of the proposed sensorless scheme is confirmed by various response characteristics.

DAN 코딩 기법과 웨이브렛 소속함수를 사용한 혼돈 시계열 시스템의 퍼지모델링

이연우,유진영,주영훈 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

In this paper, we propose a new method about wavelet-based fuzzy modeling using a DNA coding method. DNA coding techniques is known that expression of knowledge is various than Genetic Algorithm(GA) usually by made optimization technique because done base in structure of biologic DNA and optimization performance is superior. The proposed method make fuzzy system model in wavelet transform and equivalence relation after identification with coefficient of wavelet transform using a DNA coding techniques. Also, can get fuzzy model effectively of nonlinear system using advantage of strong wavelet transform about function that have sudden change. In this paper, in order to demonstrate the superiority of the proposed method compared with GA.

금속박판을 이용한 쾌속조형의 공정변수에 관한 연구

이상찬 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

In today's highly competitive marketplace, it is of great significance for the manufacturing industry to reduce lead-time and costs for the product development. Since first emerged in 1986, Rapid Prototyping (RP) technology has helped successfully to reduce time and costs. Recently, RP using functional materials like as metal have been researched. However RP using molten metal have been struggling to resolve several drawbacks, such as dimensional inaccuracy, poor surface finish, post finishing, etc., that originate primarily from the overall deposition of molten metal for each layer. So, the purpose of this study is to develop a new RP technique using sheet metal and projection welding for reducing several drawbacks in occurring RP using molten metal. And optimum process variables were determined using design of experiment(DOE).

아파트 내부의 자계강도 분포에 관한 연구

김경미,문채주 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

In recently, cancer or other health problems may be linked to a person's long-term exposure to low-frequency electromagnetic fields. But while study after study - nearly hundred now - has investigated the possibility, anomalous results make a clear conclusion elusive. A little as yet is known about how such a health link might operate or what aspects of electromagnetic fields might cause these problems. Generally the electric apparatus will affect the distribution of low-frequency electromagnetic fields based on ampere' law and will operate heath problems. In this work results of experimental investigation for residence internal section with home appliances are presented. The strength of magnetic fields shows higher than 2mG on housing internal section of the small area house with 12 meter distance to high voltage transmission line. The strength of magnetic fields shows less than 1mG on housing internal section of the middle area house without voltage transmission line. The results of study shows that the high voltage transmission lines are most impact factor. And in case of small area house, the strength of magnetic fields shows higher than that of middle area house because of home appliances close up.

현수교 캣웍 시공성 향상을 위한 Cross Bridge 설계

김호경,이재홍,최성원 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

Effectiveness of cross bridge, which connects two parrallel catwalks, is examined to increase the allowable wind velocity for the construction of main cable. Based on a rigorous nonlinear analysis utilizing elastic catenary cable elements, proper numbers of cross bridge are proposed. This procedure is expected to be applied for the actual construction for a suspension bridge with experimental data from wind tunnel tests.

A new Method for B-spline Interpolation

Jung, Hyung-Bae 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

This paper addresses the problem of B-spline surface interpolation, where the number of points varies from contour to contour. A traditional skinning approach creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion, and performs B-spline surface skinning to get a B-spline surface interpolating them. The approach tends to result in an astonishing number of control points in the resulting B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for avoiding this troublesome situation. The approach includes a novel process of getting a set of compatible B-spline curves from the given contours. The process is based on the universal parameterization allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realize efficient data reduction and provide a compact representation of a B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality.

볼 나사의 BCD 정밀 측정기 개발에 관한 연구

이춘만,임상헌 국립7개대학공동논문집간행위원회 2004 공업기술연구 Vol.4 No.-

Amongst mechanical elements, a ball screw is the most important for feeding system. The ball screw requires high precision during machining process because a machine tool demands high accuracy. The high quality ball screw can be obtained by sustaining the lead accuracy, pre-load torque, and constant ball screw center diameter (BCD), etc. In this study, we are focused on the measurement of BCD and development of precision measuring instruments for the evaluation high quality ball screw. Finally, we can control the quality of a ball screw through the measurement of BCD.